Guide device for separating yarn ends

ABSTRACT

A Duotwist-type texturing machine is modified by replacing fixed yarn separation pins with a pivotal apparatus for stabilizing the separation point of two twisted together yarns. The apparatus carries a vertically extending sensor arm with a yarn guide on one end through which the twisted together yarns pass and cylindrical yarn separation pins. Yarn snubbing angles about the pins vary compensatively to tension imbalance as the latter causes pivoting of the apparatus.

llnited StatesPatent 1191 Willis GUIDE DEVICE FOR SEPARATING YARN ENDS [75}- Inventor: Thomas Edward Willis, Martinsville,

E. J. du Pont de Nemours and Company, Wilmington, Del.

Filed: Feb. 23, 1972 Appl. No.2 228,710

Assignee:

U.S. Cl. 57/106, 57/34 HS, 242/157 R Int. Cl B6511 57/16, D02g 1/02 Field of Search 57/34 HS, 157 TS,

[56] References Cited UNITED STATES PATENTS 7/1966' Kunzle et al 57/34 HS 7/1966 Kunzle et al... 6/1967 Wyatt 57/34 HS Primary Examiner-John Petrakes Attorney-Howard P. West, Jr.

[57] ABSTRACT A Duotwist-type texturing machine is modified by replacing fixed yarn separation pins with a pivotal apparatus for stabilizing the separation point of two twisted together yarns. The apparatus carries a vertically extending sensor arm with a yarn guide on one end through which the twisted together yarns pass and cylindrical yarn separation pins. Yarn snubbing angles about the pins vary compensatively to tension imbalance as the latter causes pivoting of the apparatus.

3 Claims, 4 Drawing Figures SHEET 1 OF 2 FIG- mmmmz 3747.311

SHEEI 2 BF 2 GUIDE DEVICE FOR SEPARATING YARN ENDS BACKGROUND OF THE INVENTION This invention relates to the production of textured yarns and more particularly to an apparatus for separating yarns twisted and heat set during such production.

U.S. Pat. No. 2,987,869 describes a method and apparatus for crimping yarns. According to this method, a pair of thermoplastic yarns are separated at first and second points along their line of travel. Intermediate V the points of separation, the yarns pass a plurality of turns about each other and are heat set while twisted. This technique affords high speed production of twistcrimped yarns without the use of twisting devices. The Duotwist texturing machine is a commercial machine of this type. After being heat set in their twisted together condition, the two yarns are separated by leading each under one of two spaced guide pins. The two yarns are led to the Duotwist machine at equal rates prior to twisting and are also separated and packaged at equal rates after twisting. Normally, the yarn separation point remains fixed. and equidistant from the two guide pins. As processing continues, however, small differences in yarn tension may occur in one or the other yarns causing the separation point to migrate to one side. sufficiently, large migration of the separation point causes it to reach a guide pin whereupon process disrupting breakageof at least one of the yarns occurs. Such breakage, in actual practice, occurs too frequently for satisfactory continuity, particularly with yarns composed of more than one filament.

This problem of a migrating separation point is not new to the art and methods are known for stabilizing it. U.S. Pat. No. 3,261,155 and U.S. Pat. No. 3,395,524 are exemplary of processes and apparatus whereby stabilization of the separation point is automatically achieved by devices which respond to tension imbalance of the two separated yarns by providing counterbalancing tension effects. While these and other devices can provide excellent stabilization, their complexity and cost are drawbacks to broad utilization.

SUMMARY OF THE INVENTION An apparatus for stabilizing the separation point of two twisted together yarns advancing in a path from a source to said point for separation into two yarns for feeding separate takeup means, the twisted and separate yarns advancing in the same plane, said apparatus comprising: a support rotatably mounted on a fixed pivot between said separation point and said takeup "means, said pivot being perpendicular to said plane and in alignment with said path, said support having two elongated yarn guide members mounted thereon, said members being equispaced laterally on opposite sides of said pivot between said pivot and said separation point with their longitudinal axes being perpendicular to said plane; and an arm attached at one end to said support and extending vertically upward from said pivot, said arm having a guide at its other end through which twisted yarns pass, each of said two yarns passing in contacting engagement with and under one of said guide members as said yarns advance from the separation point to the takeup means.

The yarn guide attached to the end of the upwardly extending arm is preferably positioned from at least 1 inch to about inches above the pivot axis and formed from a customary wear resistant ceramic. The elongated yarn guide members are preferably cylindrical wear resistant ceramic pins grooved for centering of respective yarns. Their centers are laterally separated by at least 1 inch but by less than the center-to-center lateral separation of downstream roller guides in existing texturing machines, e.g., less than 3.5 inches. They are vertically positioned such that a line through the pivot axis to a lower tangent with either forms an angle of from 0 to about above the horizontal. Preferably, a counterweight is attached to the bottom of the support of mass sufficient to keep the unperturbed apparatus upright.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of known apparatus incorporating the device of this invention for separating yarns and stabilizing the separation point.

FIG. 2 shows the device of this invention when a yarn tension imbalance occurs.

FIGS. 3 and 4 are front and side elevations respectively of the device of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Known apparatus incorporating this invention is generally indicated by FIG. 1. Two yarns l0 and 10' are separately led over guides 12 to a treatment zone where they are twisted together into a bundle 20 between point 16 and separation point 18. In at least a portion of the treatment zone, the twisted together bundle 20 is heat set by exposure to a heater l4. Driven rolls 26 cooperate with nip rolls 28 to withdraw yarns 10 and 10' separately at equal linear velocities. Yarns l0 and 10' are separated from twisted bundle 20 at separation point 18 by passage through the separating and stabilizing apparatus generally designated 30. Roller guides 24 direct the separated yarns to driven rolls 26 and their associated nip rolls 28.

Referring to FIGS. 3 and 4, central to the apparatus 30 is a low friction bearing having two portions rotatable about a common pivot axis 32. A first portion 341 is rigidly attached by bolt 36 and nut 38 to bracket 37 for mounting the device in a selected position on the frame of the known apparatus. A second portion 33 of the bearing is free to rotate about pivot axis 32 and supports the remaining members of the device.

A sensor arm 31 is rigidly fastened to hearing portion 33 and extends vertically upward to support ceramic yarn guide 35. Yarn guide 35 is positioned such that advancing twisted yarn 20 makes no contact with the inner surfaces of the guide when sensor arm 31 is in its neutral vertical position.

Support plate 39 is also attached to bearing portion 33 and is laterally symmetrical. A pair of ceramic guide pins 40, 40 are fastened to support plate 39 at laterally symmetrical positions such that a line from pivot axis 32 to a lower tangent with either forms an angle of 0 to 75 with the horizontal. Preferably, each guide pin 40 has a circumferential groove 42 (FIG. 4) for guiding the threadline. Between fastener 36 and support plate 39 is an annular 44 space to prevent interference with the free rotation of bearing portion 33. It is preferred that a counterweight 46 also be fastened to bearing portion 33 in a vertically downward position. For maximum sensitivity, the mass of counterweight 46' is about the minimum consistent with keeping the whole device upright when unperturbed.

For effective separation of yarns, guide pins 40, 40 are preferably separated by at least 1 inch but should not be as widely spaced as roller guides 24 (usually less than about 3.5 inches). Yarn guide 35 is positioned at least 1 inch and preferably no more than 5 inches above pivot axis 32. As is apparent hereinafter, sensitivity of the device increases as this displacement decreases. Optimum sensitivity is found within the specified range. Whatever displacement is selected, yarn guide 35 should surround twisted bundle 20 above separation point 18. The path of twisted yarn 20 (FIG. 4) is through yarn guide 20 without contact in the neutral position but is preferably far enough forward that any slight rotation of the device immediately generates lateral contact.

In operation, yarns 10, are withdrawn at equal linear velocities and separation point 18 is normally centered as shown in FIG. 1. Inevitably in practice, however, tension imbalances occur resulting in a shift of separation point 18 to the higher tension side.

FIG. 2 shows this condition and how this invention acts to stabilize separation point 18 when such tension imbalance arises. In the situation shown, a higher tension on yarn 10 than on yarn 10' has shifted separation point 18 to the right toward guide pin 40. Shift of separation point 18 is accompanied by a corresponding shift of twisted bundle 20 which laterally deflects yarn guide 35 to rotate the whole device around pivot axis 32. At the same time, guide pin 40 rotates downwardly to increase its snubbing angle with yarn 10 and guide pin 40' rotates upwardly to decrease or eliminate its snubbing device angle with yarn 10'. As is well understood, these changes in snubbing angle act to counteract the imbalance by decreasing tension on yarn l0 and increasing tension on yarn 10' in the critical zone immediately downstream of separation point 18 (i.e., between point 18 and pins 40, 40'). Normal tension balance is thus restored.

While a specific preferred embodiment has been described, variations apparent to those skilled in the art may be made without departing from the scope of this invention. Various types of low friction bearings are adaptable to this invention and various means for attaching the elements in the device as well as for attaching the device to the frame of the apparatus are well known. It is desirable that yarn guide 35 be provided with a stringup slot in known fashion. It is essential only that guide pins 40, 40 and yarn guide 35 be supported in the geometry described so as to be simultaneously rotatable about pivot axis 32.

What is claimed is:

1. An apparatus for stabilizing the separation point of two twisted together yarns advancing in a path from a source to said point for separation into two yarns for feeding separate takeup means, the twisted and separate yarns advancing in the same plane, said apparatus comprising: a support rotatably mounted on a fixed pivot between said separation point and said takeup means, said pivot being perpendicular to said plane and in alignment with said path, said support having two elongated yarn guide members mounted thereon, said members being equispaced laterally on opposite sides of said pivot between said pivot and said separation point with their longitudinal axes being perpendicular to said plane; and an arm attached at one end to said support and extending vertically upward from said pivot, said arm having a guide at its other end through which twisted yarns pass, each of said two yarns passing in contacting engagement with and under one of said guide members as said yarns advance from the separation point to the takeup means.

2. The apparatus as defined in claim 1, including a counterweight attached to said support and extending vertically downward from said pivot, said counterweight having a mass sufficient to keep the apparatus, when unperturbed, upright.

-3. The apparatus as defined in claim 1, said elongated guide members being generally cylindrical pins having a groove for centering the yarn contacting the pins. 

1. An apparatus for stabilizing the separation point of two twisted together yarns advancing in a path from a source to said point for separation into two yarns for feeding separate takeup means, the twisted and separate yarns advancing in the same plane, said apparatus comprising: a support rotatably mounted on a fixed pivot between said separation point and said takeup means, said pivot being perpendicular to said plane and in alignment with said path, said support having two elongated yarn guide members mounted thereon, said members being equispaced laterally on opposite sides of said pivot between said pivot and said separation point with their longitudinal axes being perpendicular to said plane; and an arm attached at one end to said support and extending vertically upward from said pivot, said arm having a guide at its other end through which twisted yarns pass, each of said two yarns passing in contacting engagement with and under one of said guide members as said yarns advance from the separation point to the takeup means.
 2. The apparatus as defined in claim 1, including a counterweight attached to said support and extending vertically downward from said pivot, said counterweight having a mass sufficient to keep the apparatus, when unperturbed, upright.
 3. The apparaTus as defined in claim 1, said elongated guide members being generally cylindrical pins having a groove for centering the yarn contacting the pins. 